Filter devices having at least one filter element, which can be accommodated in a housing, through which filter element fluid can flow at a corresponding system pressure or fluid operating pressure, are commercially available and are widely used, for example in the case of hydraulic systems in system branches, through which hydraulic fluid flows. To achieve a pressure-stable design of the respective filter element, as a rule a support tube, preferably made out of a plastic material, is provided. The support tube provided with perforations and provides the support for the inserted filter material against the predefined direction of flow of the fluid. In the case of a filter device known from DE 10 2008 004 344 A1, the filter material, as a pleated filter mat, is placed about a fluid-permeable support tube, and the respective filter element is provided with end caps.
In the operation of a filter device, in particular in hydraulic systems, depending on the application, greater pressure pulsations or pressure peaks may arise. As a result, the fluid pressure prevailing locally at the respective filter element may deviate from the predefined fluid operating pressure and, in particular, may exceed that pressure resulting in damage to the filter element, in particular the inserted filter material. Pressure pulsations of this kind occur in particular in hydraulic systems having quick-closing valves or having piston pumps. When such pressure pulsations arise, the contaminate pick-up required of the respective filter element and the correspondingly adjusted filtration grade may, at times, be affected. Should this situation arise, this situation may lead to a deterioration of the filter material.
To counter this hazard, in the prior art, pressure fluctuations that arise are smoothed out by a flexible compensation device; cf. the document, U.S. Published Patent Application No. 2009/0218295 A1. In the case of this known solution, the flexibility of the compensation device permits modifying the volume located inside a filter housing, which accommodates a respective filter element. Among other things, the known solution is not satisfactory insofar as the installation space needed for the compensation device inside the filter housing is comparatively larger, so that a compact design cannot be implemented.